Well, for him to connect to your server, he's going to need an FTP client. This can be the built in command-line client, Internet Explorer, or a 3rd party client. I think the 3rd party clients are easiest to use, check out FlashFXP:
- After you install it, open it up and hit F8 for quick connect.
- Under "Server or Url", he'll need to type your IP address. Get it from here: http://whatismyip.org/
- Make sure you've got your server setup to use anonymous connections, and your friend has the "Anonymous" box checked in Quick Connect in FlashFXP.
- Hit Connect.
- It should say Connecting... in the status box, and then your files should pop up.
If it didn't work, it's probably your firewall or router. Make sure you make an exception for port 21 in your firewall, and forward port 21 for your router.